1. Field of the Invention
This invention relates to the production of transparent plastic films, sheets or strips, and particularly, to a process in which the plastic is applied, by casting when it is in the form of a solution, a melt or a reaction mixture suitable for casting, on a casting support, in continuous movement in relation to the casting, on which the deposited layer hardens and where after hardening, the resulting film, sheet or strip is detached from the casting support.
2. Description of the Prior Art
During production, by a casting process, of transparent plastic layers having very good optical qualities, the quality of the casting support surface is of decisive importance for the optical quality of layers. So far, to obtain the desired optical properties, it has proven necessary to use, as casting supports, plane glass surfaces having the desired surface quality. A process in which the casting support is a horizontal, continuous strip of juxtaposed glass plates is known, for example, from the publication of German patent DE-OS No. 27 26 159. A process in which the casting support is a continuous, horizontal glass ribbon, which is used directly at the output of its production line, is also known from German patent DE-PS No. 24 22 543.
These known processes obtain satisfactory results as far as the optical qualities of the resulting layers are concerned. However, they also have a certain number of drawbacks. Thus, in case the casting support is a horizontal strip formed by juxtaposed glass plates, the parts of the layers formed above the joints between the plates cannot be used. In the case of using a continuous glass ribbon, given the size of present glassmaking units, sufficient layout possibilities are not always available.